1. Field of the Invention
The present invention relates to Internet communications systems, and more particularly to an asymmetrical hybrid satellite-terrestrial communications network for such systems.
2. Background and Prior Art
ATMxe2x80x94asynchronous transfer mode
BGPxe2x80x94border gateway protocol
CIRxe2x80x94committed information rate
DLCIxe2x80x94data link connection identifier
EIRxe2x80x94excess information rate
EISPxe2x80x94Europe-based Internet service provider
ERTRxe2x80x94Europe-based Internet service provider US gateway
router
FRSxe2x80x94frame relay switch
IPxe2x80x94Internet protocol
IPXxe2x80x94a Novell network protocol
ISPxe2x80x94Internet service provider
LMxe2x80x94link management
NAPxe2x80x94network access point
POPxe2x80x94point of presence
PVCxe2x80x94permanent virtual circuit
REPxe2x80x94reply packet
REQxe2x80x94request packet
SCPCxe2x80x94single channel per carrier
URTRxe2x80x94router of US Internet service provider cooperating with Europe-based Internet service provider router
USISPxe2x80x94US Internet service provider
VSATxe2x80x94very small aperture terminal
The Internet is a collection of independent computer networks, which communicate with each other using standard communication protocols. By using such standard protocols, any user on any network can access any server on any other network on the Internet, subject to security considerations.
Entry into the Internet is furnished by Internet Service Providers (ISPs). ISPs operate networks that connect with each other at network access points (NAPs).
A typical network includes communication links and routing devices known as routers. A router includes tables which correlate addresses with destination information. Routing protocols are used to keep the information in the routing tables up to date to ensure that the information tables contain accurate information. Information is transmitted between NAPs in the form of individual data packets. Each packet contains an embedded source and destination address to which the packet is routed across the networks.
A typical Internet transaction involves a small amount of data in the form of a request from a user or client, and a much larger amount of data in the form of a response from the server of the content provider containing the requested information. The traffic imbalance represents a substantial waste of bandwidth in an asymmetric terrestrial link.
Many Internet users are limited to voice grade terrestrial communication lines with dial-up access, in which bandwidth is limited to 28 Kbps and 56 Kbps. Where faster data rates are available, they are very expensive. ISPs have been known to undersize their banks of telephone modems to reduce costs, and oversubscribe their service to increase revenues. This results in the inability of users to connect to the ISP during peak hours of usage and the tendency of users to stay connected longer once access is gained, for fear of not being able to get back on line, resulting in more Internet congestion.
One situation in which unequal data streams flow between requesters and Internet servers is that of Internet usage, called Web traffic, by users in Europe. Today in a nominal European country, 25% of requests on the Web are for content from within the country, 25% are for content that resides in the rest of Europe, and the remaining 50% is for content from the rest of the world, predominantly the United States. Most of this international traffic is routed via a Internet exchange point such as MAE-East, physically located near Washington D.C. When a user in Europe requests a Web page or file located in the United States, a small amount of data flows to the United States in the form of the request, and a relatively large data stream constituting the responses to request flows from the United States to Europe. Currently, the amount of data transmitted to Europe is three to five times that transmitted from Europe to the United States.
For purposes of the present description, remote ISPs are described as not being conveniently connected to the Internet. This refers to the condition of there being some inherent problem with terrestrial backbone infrastructure to meet the explosive growth of Internet traffic. United States ISPs in the present example are referred to as high volume ISPs in that their terrestrial backbone infrastructure provides capacity, connectivity and peering for Internet traffic.
The present system may in fact end up being used between infrastructures that are each rather well developed. This terminology is used simply as a context through which the present invention is described.
It is desirable to provide a system which maximizes use of available bandwidth, provides for asymmetrical use of satellite and terrestrial links and efficiently handle packets of data. The concept of asymmetrical bandwidth in a hybrid communications network using satellite and terrestrial links is known. In a known prior art system, a desktop client launches an Internet application on an IPX network. The client connects to an Internet gateway to a server using technology providing traffic management and asymmetric routing. The user sends a request to a control center over a telephone connection with the return IP address of the customer""s satellite dish. The response to the customers request is beamed to one of the satellites which beams the response back to the customer dish. The dish forwards a response to a server to an IP gateway which sends the response back to the desktop via IPX. This system meets its intended objectives. However, the present invention is intended to meet different and further objectives.
It is therefore a general objective of the present invention to provide an asymmetric, hybrid terrestrial-satellite Internet communications network and method in which use of available bandwidth is maximized and dynamically configured across points along the Internet backbone.
It is also an objective of the present invention to provide a system and method of the type described in which additional bandwidth may be provided temporarily at a selected point or points in the network either by a preselected pattern or in a condition-responsive manner.
It is a more specific objective of the present invention to provide a system and method of the type described in which additional bandwidth may be provided temporarily at a selected point or points in the network in response to demand.
It is also an objective of the present invention to provide a system and method of the type described in which permanent virtual circuits are created for guaranteeing bandwidth to a user.
It is also an additional objective of the present invention to provide a system and method of the type described in which permanent virtual circuits are created to allow provision of additional bandwidth to a user when excess system capacity exists.
It is also a further objective of the present invention to provide a system and method of the type described in which permanent virtual circuits are created for the purpose of broadcast or multicast.
It is also an objective of the present invention to provide a system and method of the type described in which scalability is provided by assigning more permanent virtual circuits to a network or by assigning more bandwidth to a specific permanent virtual circuit, whereby a user network may be readily upgraded.
It is an additional objective of the present invention to provide a system and method of the described in which a border gateway protocol is used to exchange data to and from the Internet.
It is another objective of the present invention to provide a system and method of the type described in which redundant or alternative paths are provided should a link become disabled.
It is also another objective of the present invention to provide a system and method of the described in which a border gateway protocol (BGP) is used to control routing of data in the hybrid environment to aid in providing redundancy as well as normal routing in the hybrid environment.
It is still another objective of the present invention to provide a system and method of the type described in which terrestrial routing between a satellite earth station antenna and an ISP is optimized.
It is another objective of the present invention to provide a system and method of the type described in which terrestrial satellite links a connected to a closest point of request on the requesting backbone.
It is a general object of the invention to provide a system and method of the type described which connects to the backbone structure of the Internet, and which an ISP may view as an overlay on his system without need for the ISP to purchase additional capital equipment.
It is a general objective of the invention to provide a system and method of the type described which connects to a backbone of the Internet, and which an ISP may view as a complimentary enhancement of the ISP""s backbone.
Briefly stated, in accordance with the present invention, low-cost, high performance access is provided to an Internet service provider (ISP) on a group of Internet service providers (ISPs) not convenient to a high volume Internet exchange point through a flexible hybrid terrestrial-satellite Internet communications system and method. The innovative hybrid system of the present invention employs at least one satellite and preferably a multiplicity of satellites, for example a constellation of satellites.
Exemplary embodiments of the present invention comprises a hybrid satellite-terrestrial Internet communications system and method that provide high volume connectivity between an Internet service provider (ISP) and a remote customer site that generates a request for content to be supplied by the ISP. In an exemplary system, a first gateway processes a request for content generated at the remote customer site and routes the request. A second gateway processes the request for content routed by the first gateway to route the request to the content provider. One or more satellites are used to transmit requested content supplied by the ISP to the remote customer site. An exemplary method comprises the steps of generating a request for content at the remote customer site, processing the request for content to route it to the content provider, and transmitting requested content supplied by the ISP to the remote customer site by way of one or more satellites.
An illustrative embodiment of the present invention includes the request for content routed by way of a terrestrial communications link, which comprises the Internet. The request for content is routed to the ISP by way of the one or more satellites. The transmitted content is received directly at the remote customer site. The requested content may also contain statistically multiplexing information packets comprising the requested content into permanent virtual circuits (PVCs) that maximize bandwidth usage. The requested content is routed to the remote customer site by way of a gateway or other point of presence (POP) site.
Asymmetric hybrid circuits are advantageously used to most efficiently handle the resulting asymmetry from low volume requests and high volume responses. By way of example, a request from a user is coupled via routers and servers to a point of presence (POP) of an ISP in a group. The group ISP POP also includes a gateway coupling the group ISP to a terrestrial link which has an opposite end for coupling to a high volume ISP. Requests are directed to the high volume ISP through a POP on the backbone of the high volume ISP, and responses are provided. Response information packets are highly statistically multiplexed by one or more routers into permanent virtual circuits (PVCs). In a hybrid network provider POP, switch means impose committed information rates on each PVC, the committed information rate comprising a guaranteed minimum bandwidth for its associated PVC. Known protocols are used in an unexpected manner to manage the switch means. Additional bandwidth may be assigned temporarily to a PVC. PVC burst capability is also provided. The hybrid network provider POP delivers signals to a satellite uplink. The satellite delivers signals incorporating all transmitted data to each POP in the group of ISPs. Routers coupled to each group ISP POP filter the downloaded satellite signals to direct responses to corresponding requests. Multicast or broadcast from the hybrid network provider POP may be provided. If either the satellite link or the terrestrial link is disabled, communication may be diverted to the other link. Management of transmitted bandwidth may be performed in a two-way terrestrial or two-way satellite network configuration. Redundancy is thus provided.